Hexokinase and glucose-6-phosphatase activity in woodchuck model of hepatitis virus-induced hepatocellular carcinoma

Abstract

2-Deoxy-2-[ 18F]fluoro- d-glucose ([ 18F] FDG) is used for PET imaging of woodchuck ( Marmota monax) model of hepatocellular carcinoma (HCC). The usefulness of FDG on this animal model needs to be validated according to the hypothesized mechanisms. In this study, two key enzymes involved in glucose or [ 18F] FDG metabolism, hexokinase (HK) and glucose-6-phophatase (G6Pase), were examined for their enzymatic activities in the woodchuck models of HCC, which has not been studied before. After dynamic PET scans, woodchuck liver tissue samples were harvested and the homogenate was centrifuged. The supernatant was used for HK activity assay and the microsomal pellet was used for G6Pase assay. HK and G6Pase activities were measured by means of colorimetric reactions via kinetic and end-point assays, respectively. Total protein content was measured by the Bradford method and used to normalize all enzyme activities. HK and G6Pase activities in woodchuck HCC will be used to correlate with in vivo PET imaging data. The woodchuck model of HCC had significantly increased levels of HK in the livers compared to the age-matching healthy woodchuck (7.96 ± 1.27 vs. 2.74 ± 0.66 mU/mg protein, P < 0.01) and significantly decreased levels of G6Pase compared to healthy woodchuck (40.35 ± 19.28 vs. 237.01 ± 17.32 mU/mg protein, P < 0.01), reflecting an increase in glycolysis. In addition, significant differences were found in HK and G6Pase activities between HCC liver region (HK: 7.96 ± 1.27 mU/mg protein; G6Pase: 40.35 ± 19.28 mU/mg protein) and surrounding normal liver region (HK: 2.98 ± 0.92 mU/mg protein; G6Pase: 140.87 ± 30.62 mU/mg protein) in the same woodchuck model of HCC ( P < 0.01). Our study demonstrated an increased HK activity and a decreased G6Pase activity in liver of the woodchuck models of HCC as compared to normal woodchuck liver.